As you investigate, consider a new traveller from Garhauer. You may want to look at another thread on this forum:
https://www.pearson323.com/forum/index.php/topic,245.msg1622/A new traveller will provide significantly more mechanical advantage, lower friction (i.e. less effort), and is an all-around pleasure to use. It is not that much more expensive; my traveller blocks began to fail, and I inspected the blocks on the car as the control blocks, I realized the whole setup was slowly breaking up - the delrin in the sheaves was cracked in all of them.
Rig-Rite has the parts (and as Ed says, not very responsive), but at a price; Garhauer offered a brand-new setup, customised for Selene, and drop-in. The question for me ended up as - okay, I could get the parts to refurbish the old traveller - but if I did, I would end up with the old, cumbersome design, difficult to use, but some newer components. Or...
Heck, I even told Garhauer they could keep my old rail to use as a template in case other folks needed it!
Just sayin'!