CartMods.com was able to quickly create a mod that did this for me. Hopefully they'll add it as one of their standard mods, but if not, I would highly suggest contacting them and asking for this one. Having encountered so many unhelpful online businesses, it was a refreshing experience to deal with such prompt and polite people!
I now have the ability to set a unique title, meta keywords, and meta description for each product. This is absolutely invaluable for good search engine rankings, and EVERY cart should be able to do this.