Need a 4" Tall Seat

To get my eye to the polar alignment scope on the Losmandy, I need to sit about 4.5" above ground level.  I tried kneeling and stretching from ground level without success.

The obvious answer is a 4" x 4" cut into three pieces, glued together with expoxy to produce a 4" x 24" x 4" platform.  Adding a back would be nice but I do not expect to spend more than a couple minutes aligning on Polaris.  This is obvious, cheap, and readily available, although because a 4" x 4" is really 3.5" x 3.5" it will require a little stretching to get in position.  Can anyone think of a readily available 4" tall device intended for some other purpose that is not too expensive or heavy?  Are ammo cases that thickness?

Yes.  I bought a steel ammo can recently that is 4" thick and about 10" wide.  Three of them would likely do the job and they can be repurposed for holding ammo.