Just a heads up as I've dealt with needing two sets of these spacers in 1 inch to clear aftermarket T&D Rockers.
First off I do think it should be presented to a vendor as once again we pay fees here to have group buys and sell parts. Not trying to be an ass at all, but if that's the case then we shouldn't have vendors and it be a free for all as far as selling parts on here.
That being said, there are a couple ways of doing these and made in small quantities usually costs out the rear! I had a set drawn up using 1" 6061 aluminum and the amount wasted to produce these is what cost so much as well as machine time. I was quoted $670 for a pair as I had drawn up. After feeling discouraged and taking the drawing a few places for quotes I decided to but the EBay/other Vendor valve cover spacers for $300.
Well, low and behold they're not machined for the O ring stock gaskets. Therefore you use sealer between spacer and head and its guaranteed to leak at some point
( it did after 2 months)
The more expensive sets that were made years ago did indeed have the stock valve cover gasket machined into it to seal just as the valve cover does stock. Needless to say the last set of T&D rockers installed was also quoted the $700+ for an o ring machined set of spacers that worked great! Problem is that's very close to a complete set of valve covers which indeed look better than stock with spacers. I think if you wanna design something to produce, valve covers would be a better use of the aluminum and labor time.
Just my .02