If you want a pair of stable stands for L-seats, planche training, handstands, etc, the P90X stands are very stable and work well.
They are a little pricey @ $50, but worth it IMO.
Two small warnings:
First, these are not really actually made to be used for this purpose (they are made for pushups). However, I weigh ~215 and feel very comfortable that they can support my weight.
Second, they are angled; not straight.
http://www.amazon.com/Beachbody-P90X-Po ... B003JTZ3YM
Anyway, I found them to be worth the $50.
EDIT: Here are some straight (not angled) stands. They are 7" tall, so maybe not tall enough? I have not used these (I have the ones above).
http://www.qvc.com/qic/qvcapp.aspx/view ... ite=F09207
