The only source I’ve seen for the Croation 22 LR Grizzly conversion is centerfire systems. Centerfire Systems sell the conversion kit and spare magazines. I’d be surprised if there are any spare parts available for purchase but if there are Centerfire Systems might be the source.
The magazine used in the Croation Grizzly 22 LR conversion appears to be proprietary. The only other place I’ve seen a conversion produced for a similar style of AK 22 LR conversion was Jonathan Arthur Ciener. I have no idea if the Ciener magazine are compatible with the Grizzly. I believe the Ciener AK conversion is out of production and have no idea if Ciener parts would fit the Grizzly.
The other AK derived 22 LR guns do not share magazines. The Romanian AKT-98 was supplied with a Weger style ten round mag and WASR AK-22 came supplied with a polymer ten mag. Black Dog Machine manufactures a magazine for the AKT-98/WASR AK-22.
The GSG AK-22 uses a proprietary mag as does the Marlin Blaze 47 (AK-22). The Armsor AK 22 LR rimfire and the Italian manufactured Armi Jager Mitchell arms imported AK-22 used a proprietary magazine.