Jersey's and Holsteins are going to be pretty big for an acre. You will spend a fortune in hay to feed them. They will also outproduce your needs... I'd keep looking for a mini of some dairy variety.
The Dexter website does have breeders listed by state:
http://www.dextercattle.org/adca/adca_directory_ads.html
Or, you can contact the director for your region, and they should be happy to help:
http://www.dextercattle.org/adca/adca_officers.html#rd
Dexters are a little-known treasure, and everyone involved with the breed is happy to help. I have dealt with lots of different people, both at the ADCA and at shows/sales. EVERYONE has been awesome, with the exception of one hoighty-toighty breeder in VA. Who basically said I wasn't qualified to own one of her animals. Ohhhh kayyy.