Rob- not sure what you mean by surface mount, but I found a sink faucet with a shower diverter at my local RV dealer/part supplier. Here's a link to their catalog which I actually think is more of a national RV supplier parts catalog. Look at the one on the bottom right hand side of the page. Hope it helps. GO-RV.com - RV On-line Catalog
Edit- I see now you're asking about a bath faucet not sink. The catalog I linked to has many options, maybe what you need is in there.