This Conti Comfort Kit is what a lot of people use. Several car manufacturers include this kit with their cars that don't have spare tires.
http://www.tirerack.com/accessories/detail.jsp?ID=38
More info:
http://www.continentaltire.ca/www/do...ort_pdf_en.pdf
This one is basically the same but half the cost. Consumerreports said it's basically the same as the conti kit but took slightly longer to fill the tire.
http://www.amazon.com/gp/product/B00...9NY511YSB75Z6N
A bonus of these kits is that you get a compressor to keep your tires or other inflatable items around the house inflated properly.
BMW has their mobility kit but it's around $130.
Some sealants are safe for use with TPMS, others are not so that's something to watch out for.
The cans work too but aren't as easy to use and there's a slight risk of the pressurized can exploding in a really hot trunk. CR testing also showed the cans don't do well sealing large nail holes, but are ok for smaller holes.