I bought from Rallispec, upon recommendation of board members and was completely satisfied.
I recently bought another set while doing my transmission swap. This time I noticed that many vendors, including eBay vendors etcetera, are selling Group N mounts.
When I asked Rallispec about the mounts and the market, I got a next-day response that was personal and thorough. I again chose Rallispec, despite a slightly higher price, because of their response.
Subaru of America now sells upgraded mounts under their SPT brand and therefore anyone can purchase these through any dealer. Thus there are many places you can buy them from. However, SPT uses a different part numbering system from STI and many times we have found that STI has re-engineered the product to suit the US market or to avoid litigation concerns (they know that everyone sues everyone in the US!). In the case of the mounts its unclear if they are exactly the same as the STI Group N ones or not. No one has really tested them against each other. But other shops are selling them as STI Group N regardless. If you get a mount with an STI label and a part number that starts with "ST" you have a genuine STI part. If the label is a Subaru label and does not start with "ST" then its an SPT part.
We have and continue to buy our parts directly from Japan so we only sell genuine STI parts....not rebranded SPT ones.
Although Rallispec acknowledges that they are merely unsure if the parts are the same, I appreciate their concern and am happy to support their efforts to ensure they sell legitimate Group N parts.
Here are the mounts I received from Rallispec. Clockwise from top-left: 5MT Transmission Mount, Pitchstop Dogbone, RH Motor Mount, LH Motormount