I made ones for mine a few months ago, because I had longer shocks and I needed to make sure they weren't the ones doing the stopping when compressed. I made some "provisional" ones which were blocks of wood put inside the spring. The rear were 4 cm, and they are from a tree trunk more or less the same diameter of the spring (a cm or two less). They've been there ever since, and they've worked perfectly, so until they rot or something they will stay there. For the front they were 2cm, so I had to tape them to make sure they didn't slide between el coil wire when fully extended.
Just an idea!
