What's it look like? This one is for a BBC, https://www.amazon.com/Parts-Place-...sed-search-10&pf_rd_t=BROWSE&pf_rd_i=15726921 Ever think of just eliminating it?
That is the part but only 2 bolt holes. I saw some sections to delete but not BBB. Head pipe too close without.
Mix up some very thin oil with graphite to lube the shaft. The lube will go away but the graphite stays and may prevent sticking.
Hector may have a few left. https://www.v8buick.com/index.php?threads/heat-riser-valve-delete-updated-6-28-2020.181056/