I'm looking for some options for a 4.5" 22lr upper with a handguard I can fit my Prodigy under.  Any ideas or recommendations?

Taccom 4" with pretty much any 7" rail you want.

This! I used a taccom 4" plus sparrow under a 7" Noveske NSR.

Another for Taccom, I have the 4.5".

Though mine is bar and I just put my outback II on the end.

I went with a CMMG 4.5" as I already have a CMMG 6.5" upper.  Forearm is YHM quadrail.
 







 

I have a beyer barrel that I use with my sparrow, great setup that works for me

This is a 7" UTG Super Slim  over a 4.5" TACCOM barrel and Spectre II. Although the TACCOM barrel doesn't need it to mount the Spectre II, this one has a SiCo adaptor that allows for the o-ring engagement. I only mention it because it adds about an inch to the OAL in the photo. I tried the UTG after a buddy bought one and I got a look at it. I have to admit that I thought I wouldn't be very impressed with this sub 100 dollar handguard/rail, but after giving it a good look during the install and then using it for a while, it's not going to be replaced.

I have a 10.5" Spikes upper that I bought new from Spikes Tactical around four years ago. I'm told they don't make them anymore. My Spikes upper has been great, in fact I use it for NSSF Rimfire matches. It pretty much never lets me down.

I've been out of the loop on the latest developments with rimfire uppers, but after seeing this thread I'm curious, are the TACCOMs the new standard? Are they reliable and well built?