Although the Church prohibits the selling of relics, it is my understanding that blessed items may be sold, but only for their intrinsic value; no value may be added for the blessing itself. It is quite common for churches that are closing to sell religious art and furnishings, even the altars to other churches. A local church recently acquired a new altar in this way.
It’s difficult to get a parish to part with anything liturgical that has real value because, canon law restricts a pastor’s ability to alienate (ie “sell” or “give”) the temporal goods (“property”) of the parish. It might seem like a simple thing “the pastor doesn’t use it, he doesn’t want it, so he’ll be willing to sell or give it” but it just doesn’t work that way. For items that are actually valuable (we’re not talking selling cupcakes) there are restrictions on what the pastor can and cannot do on his own authority. Keep in mind that these laws are in place to protect these items from going to the smelter. The Church learned a hard lesson during the Bolshevik years in the 1970s when all beauty was obliterated (and the law was ignored). Thankfully, bishops are more aware today, and more likely to protect the Church’s patrimony.
Here is a website which specializes in brokering the sale of such items from church to church, with the goal of preserving their sacred use.
While not used, I would recommend www.autom.com as an option. They are much less expensive than the local Catholic goods store.
What I can do is provide some bookmarks. Nothing here should be taken as an endorsement. I also feel I must mention that some of these sites are nothing more than bookmarks of sites I’ve learned—meaning that just because I have a bookmark doesn’t mean I’ve actually done business with them. That’s just a general reminder that one should use caution and common sense when making purchases over the internet, so use a trusted payment method that will protect one’s financial security.