Try e-gunparts.com
Remington's website has what you are looking for.
25-65 USD
Can I shoot 380acp caliber out of my 32 pistol?
http://stevespages.com/ipb-remington-51.html
In excellent condition, about $500.
50-175 usd
Yes, that would be the Model 51 made in 380 and 32 auto.
Manufactured 1919
Condition?
There are several DIFFERENT .32 caliber cartridges. The .32 bullet is smaller in diameter than a .380. SOME .32 cartridges are longer, and have more power, such as the .327 magnum. And some .32 pistols are smaller than some .380 pistols, and vice versa. The caliber has nothing to do with the size of the gun.
What caliber? 22, 25, 32, 380, 9mm?