There are a number of different 1911 CO2 airgun models sold under license by Umarex.

For the non blowback German made 1911 models that take the 8 shot rotary magazine click here.
For the blowback models there are two main – the easiest way to distinguish these is to look at the colour of the CO2 seal in the magazine – it will be white or green:

For white seal models (like the below) – please use this link for parts

For green seal versions (like the below) please use this link for parts.