What choices do we have on Clear resins for DLP?
Formlabs sells a completely clear resin that they've even made simple lenses from, but it's about $150 for a liter. I have no idea how well it would work with your DLP setup. Looks amazing in the pictures though. 

MatterHackers sells PhotoCentric UV Firm Clear for $90 for a liter as well. It's not quite as easy finding pictures of this stuff, but from what it looks like, it's still pretty decent. Assuming you've got a UV DLP 

Disclaimer, the PhotoCentric stuff says it's a UV resin (10nm to 400nm IIRC) and I have not the slightest clue what Formlabs designs their resin for, so YMMV.