Item #1--- Tie-downs...

go to your local big-box or whatever hardware store, purchase 10 stakes
(12 in. long, 1/2 or 5/8 in in diameter)
why 10 when you only need 9? Because you'll lose one.
cost? about $10. IF you have the equipment (I don't), you can
buy rebar or similar and cut to 12-18 in lengths
at the same store, get a heavy duty plastic hammer - about $2.00
while you're at it, if the store has marine-quality rope, get 3 lengths,
appropriate to your wing height. I have a low-wing cherokee, so
the back tie-down only needs 6 feet at most, the 2 wings, 10 feet each.
the rope needs to be 1/2 to 5/8 in
and wander to the chain area of the store and find the heaviest duty
chain link they have. get 3 set of 4 links. cost - about $3.00 total
if you really want to be spiffy, get a nylon bag to put this all in.

total cost? about $15 + the rope. I bought the rope at the local
marine shop, and bought more than I needed, so you could probably
get by with $20 for a low-wing.

I used this at OSH during the Sunday (Monday?) storm - no problems!

Putting it together...3 stakes go thru 3 of the links on the chain
(or 2 stakes if it's not windy) and the rope goes thru the last
chain. I used an interior chain for the rope so that it would be
easier to get the stakes out of the ground (pull from the middle...)

Item #2 -- glareshield...
In the very near future, the edge (about 3-4 in. wide) of the glareshield
will be completely covered in black velcro. Why? Everything goes up
there and stays there! The handheld GPS (garmin pilott III), the
TPAS, LED flashlight, pen/pencil, etc. No more fumbling around trying
to find something --- it's right there in front of me!

Item #3 -- something to put the O2 mask and/or nose thingy...(cannula)
I leave the hose connected to the O2 tank, then loosely roll the hose
and put the excess and the mask into a large zip-lock plastic bag.
Close the bag up to about 1/2 in and tuck it into the handle of
the O2 case. I've got an Aerox unit in a padded case that is attached
to the right pax seat so I can always reach it. The zip bag fits nicely
into the carrying handle.
Always handy, always clean.

Item #4 -- packages of alcohol wipes.
No, I'm not completely paranoid about germs (well, not yet). But I
frequently have friends, once in a while an Angel Flight. So I keep the
headseats scrupulously clean. The wipes clean off the ear muffs, the
mic and the foam cover on the mic. Got this idea from the museum...
I volunteer at a local museum and do multiple shows for the visitors.
We use wireless hand mics and headsets. So we keep the wipes handy
for the mics, and the spray for various exhibits. Sams club or costco,
100 or 500 in a box for almost nothing. (these are the same wipes
used to "clean" before an injection or blood draw, about 1 inch square)

Item #5 -- under seat storage.
Turns out that the space under a seat in an older cherokee is just bout
the size of a 500 sheet (ream) box of paper. Took the box, reinforced
it a bit with tape, and it's a perfect place for the fire extinguisher,
the CO detector, the "big" flashlight (metal, 3 D size batteries).

Item #6 - the user manual.
The previous owner gave me an 8.5 x 11 binder with everything in it.
Not practical.
Once again, suitable for an older cherokee. The width of the area
between the handles on the yoke is EXACTLY the size of a small, 6x9 in.
plastic clipboard at the local office supply store. The
pressboard won't work, since the clip extends past the edge of the
board. The plastic one has the clip within the boundary of the board.
I rewrote all the procedures, frequently used freqs, checklists, etc
and printed them 3 x 4 in. Over to Kinko's, laminated and spiral
bound it. Fits perfectly on the little clipboard, again, right
in front of me, no hunting for anything. Cost? About $1.00 for
the clipboard and whatever Kinko's charges for laminating and binding.
One side of the little notebook is under the clip, the other side
is held on with a heavy-duty rubber band. Clipboard just slides right
into the yoke.

Item #7 -- AR(R)OW holder.
Back to the office supply store. Small, transparent plastic folder
(letter-size envelope). More velcro. One side of the velcro on
the envelope, the other on the back wall, high up by the headliner
(that way, it won't be dislodged by luggage or gear). Absolutely
visible to everyone at any time. Cost? Another $1.00 IIRC.