For your Model 1906, try here:
Firearm Parts and Accessories | Numrich Gun Parts Corp. | e-GunParts.com
If that was not a typo, and you have a .25 RF, that is not a .25 LR, it is a .25 Stevens Rimfire- and I wish you the very best of luck in finding ammo- it has been out of production a LONG time- and no, you cannot shoot .22 ammo in it. But the sme source (gunpartscorp,com) MAY have what you need, If it is not listed, email them. They sometimes have parts (a few) and they don't list them.