Someone has asked me to mend an Ultima 10 which requires a new seal as above. Where do I get a replacement "O Ring Seal" that fits in the Barrel and Seals to the Pellet Seating Probe ? The current one has a break in it, none of my Spares Kit O Rings are the correct size, and a Web search hasn't led me anywhere useful.

All informative replies appreciated,

Thanks, Vic Thompson.