This is a great idea. However....
Bought the 80 cent picture frame from walmart. Couldn't find anywhere that sells a plastic cutter like the one the OP mentioned. Read somewhere in the interwebs that acrylic can by cut like traditional glass. So I used a glass cutter with one of those tiny scoring wheels: fail. Ended up breaking the picture frame beyond salvage. Luckily I bought two extra 80 cent frames as backups.
The next day I located said plastic cutting tool at home depot and was able to make the required cuts. Being the perfectionist that I am, I really took my time to make sure that I wouldn't destroy the remaining two frames. Cuts ended up perfect with a bit of sanding and filing.
Then came time for the bending. With my trusty heat gun, I proceeded to heat, bend, and deform the 2nd frame into a wavy abomination vaguely resembling a tortilla chip...*sigh*. Being careful not to destroy the 3rd and final frame, I was able the coax the acrylic into bending 90 degrees without too much deformity. It's definitely not pretty, but at least this 3rd attempt is a functional gel holder.
My point is this: I love to do DIY projects like this, but sometimes it ain't worth the time and effort compared to just buying already made.
Sorry to make my very first post on this forum long and negative, but I just had to vent.
Carry on!