No, Toni. Multiflora doesn't work against nematodes.
Nelsons' Florida Roses is the main retailer of roses grafted onto Fortuniana, Roly. They have a fairly broad selection, and I'm not sure how many Austin roses they have, but I know they have Abraham Darby. Their prices might sound high, but when you add longevity to your calculations, roses from anyplace else would cost a lot more.
http://www.nelsonsfloridaroses...
Another place offering roses grafted onto Fortuniana is K&M Roses in Mississippi. I've bought several roses from them because Fortuniana works really well in California too, and it doesn't appeal to gophers, which are my nematodes.
http://www.kandmroses.com/