Sadly, Slickwraps’ pricing is even worse.
Skinit has no Framework-specific offers, but their universal one is more reasonably priced.
Gekaskins does offer universal laptop skins, too, but sadly only up to 15" (389 x 247mm).
Any other alternatives?
Edit: more (possible) alternatives:
DecalGirl
The Wrappz customizer sadly says, that the required size for the FL16 isn’t available. 
Uniqfind doesn’t seem to offer Framework skins yet and has no custom option.
MightySkins
Here’s a list with dbrand competitors.