Anything similar in today's production to the dimensions of the Colt Diamondback that isn't going to run me $1900 as a collector's item?

Appreciate just a similarly sized production gun for reasonable cost.

Ruger SP101 comes in 22.  LCR.  So does the GP100 but it's a bit large.  Smith 18 if you can find one. Smith also makes J-frame 22s but the model number escapes me. If you want to go cheap an old High Standard Sentinel.  Older Charter Arms Pathfinder.  Taurus has made both K and J frame sized 22s.

looking for 38 special

My bad.  Smith 15/67. Smith 686 for a bit larger package.  Ruger GP100.  Older Ruger Security Six.  Older Colt Trooper.

Plenty of older used stuff out there that will save you some coin.

The new Colt King Cobra Target is the same size and shape as the .38 Diamondback, only the shape of the trigger guard is slightly different.
The action is all new and not like the old Colt "D" frame models.

I'm expecting Colt to offer it in a .22LR and call it a Diamondback.

The new Cobra, King Cobra, and King Cobra Target use the same size frame and cylinder as the old Colt "D" frames like the Detective Special and Diamondback but with a modern transfer bar ignition/safety system.

https://www.colt.com/detail-page/king-cobra-target