yeah you want to find them second hand because those would set you back a lot of money new (way over £100). Some guy was selling some on ebay way cheaper than that.
However, if you are planning to fit 748R TBs to any desmoquattro other than 748R the inspections covers will not suffice. You also need to skim some bits of the heads.
Alternatively, you may put some spacers that push the manifolds by a couple of mm and make that set up work. I ran into the same problem in the past and got such spacers made. I produced a small series so can sell you some if you need.
Threaded Mode