It seems harder to find 25.4mm stems! Hadn't thought of trying without a shim, will give that a go before I try anything else, would like to use this stem if possible!
Get a proper shim. I have always used Nitto cos they're reasonable on trade, but I'm sure there are cheaper ones - I haven't had any problems with them as they're two part and rigid unlike beer can shims.
It seems harder to find 25.4mm stems! Hadn't thought of trying without a shim, will give that a go before I try anything else, would like to use this stem if possible!