Unless they are part of some subassembly the tool builder bought and installed then your only source is usually the tool builder. If you can identify it as an after market item, you may be able to find an alternative source. The only other possibility would be someone making these as replacements if they break/fail often enough.
I feel your pain, I have managed to find some parts from alternative sources for 1/2 to 1/4 the price from the dealer/tool builder. Usually after buying them for full price at least once.