Do you have variegated in your area? Dalmatian doesn't come specifically from a modified hooded gene, but rather from the variegated gene. These genes are all on the same locus, but different. If you have variegated, you can get dalmatian, it will just take some selection over a few generations. You don't even need a good variegated you can start with a "variegated" with lots of color (sometimes called "varie-berk" or mismarked "berkshire"), and just select for more white over the generations. A high color variegated bred to a berkshire (especially one with more white) or a hooded can work to get you more white in subsequent generations. You might also end up with capped out of variegated, or you can breed variegated to capped to get your dalmatians.

I'll have to get some pictures, but I've got lots of white on my rats now (variety of markings, ranging from hooded to variegated to capped and some resembling dalmatian, though not good ones because I haven't selected specifically for that pattern). I started with a couple hooded, high color variegated, and berkshire.