Before you move on to another project due to lack of parts you might want to contact Randy Boadway at eRockets and ask if they either have or can make up what you need. I visited eRockets a couple years ago for one of their infamous Tuesday WSR club build nights and during casual conversation about some oddball centering rings I needed for a scratch build they offered to make them on the spot! Unfortunately I couldn’t recall the exact dimensions I needed (I ended up making my own at home for that project, which crashed spectacularly). It’s at least worth a quick email to find out.