Though not a 510 connector, a standard KR808D-1 battery is small, simple, just use a normal 808 carto on it. 808 has a higher voltage than you'll get on a small 510, and they are good for a couple hours' use between recharges.
A cheap way to try it is a vapornine nebula starter kit. About $8 (and decent shipping), gets you one auto battery, USB charger, 2 prefilled cartos (either tobacco or menthol, 16mg). The cartos are easy to top off, if you have a tobacco or menthol that you like, else just buy a 5 pack of them from somewhere else. Battery with carto is only 4-3/8" long, 1/4" diameter (no wider than the carto).