I've successfully matured seed on teosinte in Maryland -- but I had to cover the plants with black trash cans to artificially shorten the daylength. I put the cans on a few hours before dark and took them off a few hours after sunrise. I got the idea from these articles:
Teosinte Article and
Another Teosinte Article I wouldn't worry about giving the plants special soil or watering. They grow pretty well in normal garden conditions. As for keeping outside pollen from contaminating your teosinte, the offspring would definitely be recognizable as different, if unintentional crossing did occur. I did intentional crossing and the offspring were very different from teosinte. I would just try to make sure lots of teosinte pollen gets to the silks and hope for the best. Or you could cover individual ears with aluminum foil and hand-pollinate; I've done this with corn and had decent results.

By the way, I started the my teosinte indoors and then planted the already started seedlings outside when weather permitted.

I am interested in growing a small amount of Zea Mays ssp. Parviglumis. Does anyone know of a seed source?

You can request teosinte germplasm from the USDA-ARS, or order it from nativeseeds.org. Nativeseeds is currently out of stock, but when I last contacted them they said they expected a viable crop sometime this fall. I'm not sure what species of teosinte they offer, probably Zm ssp. parviglumis, ssp. mexicana and/or Zea diploperennis. If you're involved in some sort of legitimate research, you'll probably want to go the USDA-ARS route, as they have actual wild collected material available, with all of its wild allele frequencies intact. To order germplasm from the USDA-ARS, go to http://www.ars-grin.gov/npgs/acc/acc_queries.html scroll down to the taxonomy query, and do a search for 'Zea mays subsp. parviglumis'. Also note, there are some Zm. ssp. parviglumis accessions still listed as 'Zea mays subsp mexicana'. You can view a description for each accession. Any Zm ssp. mexicana accession that is described as 'Race Balsas' is actually ssp. parviglumis. Each accession has an availability status, look for one that is currently available (probably 100 seed distribution). Once you've picked an accession ID, go to http://www.ars-grin.gov/npgs/order.html and fill out the form. At the bottom where you choose what repository to submit the order to, select 'NC7 - North Central Regional PI Station'.

You can request teosinte germplasm from the USDA-ARS, or order it from nativeseeds.org. Nativeseeds is currently out of stock, but when I last contacted them they said they expected a viable crop sometime this fall. I'm not sure what species of teosinte they offer, probably Zm ssp. parviglumis, ssp. mexicana and/or Zea diploperennis. If you're involved in some sort of legitimate research, you'll probably want to go the USDA-ARS route, as they have actual wild collected material available, with all of its wild allele frequencies intact. To order germplasm from the USDA-ARS, go to http://www.ars-grin.gov/npgs/acc/acc_queries.html scroll down to the taxonomy query, and do a search for 'Zea mays subsp. parviglumis'. Also note, there are some Zm. ssp. parviglumis accessions still listed as 'Zea mays subsp mexicana'. You can view a description for each accession. Any Zm ssp. mexicana accession that is described as 'Race Balsas' is actually ssp. parviglumis. Each accession has an availability status, look for one that is currently available (probably 100 seed distribution). Once you've picked an accession ID, go to http://www.ars-grin.gov/npgs/order.html and fill out the form. At the bottom where you choose what repository to submit the order to, select 'NC7 - North Central Regional PI Station'.