Welcome!
With regard to light sources...
See this post herein:
https://www.photrio.com/forum/threads/diy-uv-box.180065/.
Also see:
https://www.alternativephotography.com/diy-uv-light-boxes-alternative-photography/
These 395 nm LED strips are very easy to use and inexpensive. They work well for all processes except direct to plate photo polymer gravure which require 360 nm LEDs. For a 16x20 unit, I would use 8 of the 24" long strips.
With regard to print frames...
There is lots of good information (about both DIY and commercially available frames) in the alternativephotography.com link above. You'll need to scroll way down the page past the light box stuff.
Photographer's Formulary makes nice frames with two different methods of closure, see:
https://stores.photoformulary.com/contact-print-frames/. These are sometimes in stock at B&H with free shipping.
I prefer the swing arm style but went with the snap back style for my 16x20 frame because of the cost and the fact that I don't make a lot of prints that large. The snap back style works just fine but it can be tough on my old, arthritic fingers. If I was to buy another one I would go with the swing arm style. (The rest of my random collection of smaller frames are the swing arm style.)
The key to a print frame is to insure that there is good contact between the negative and the sensitized paper. One can fine tune the pressure, if needed to get good, uniform contact, by adding a sheet or two of 250-300 gsm paper to the 'sandwich'. This is sometimes needed with thin sensitized paper and with the larger frame sizes. I just leave the extra paper (sized to fill the frame) in my frames (both 11x14 and 16x20) for every exposure.
Regards,
--- Frank