As someone who's been selling them parts for almost 30 years I can say that sometimes the problem are with their suppliers.
They don't make parts, they buy them from vendors and sometimes (especially lately) the supply issues are caused by the vendor being out of the part or the materials to make the part.

They buy the aluminum 4 speed shifter mounting brackets from me that I've been reproducing since about 1992.

They usually order some after the 1st of the year so I contacted my casting company in early December and was told it would be at least 6-8 weeks before I would get the casting from them to machine.
Usually it's just a couple weeks to get them from the casting company.

If they make an order (Year One), I'm at the mercy of the casting company right now.