if you don't mind simple, planoconvex quick and dirty
you can make your own barrel lens from supplies found
at the suurplus shed. i have made lenses that can " illuminate "
20x22 with ease ... corners will soft, you can probably make your own
fstops and get better illumination ...
if not reversed ( flat out curved towards film ) it will be a plain old lens
if reversed it will be like a wollaston meniscus, a low budget of what
reinhold makes ... and i think he is making some very large ones these days ...