You could try rooting cuttings from the plants you no longer have seeds for.

Just pot them up into bigger pots, all the way to gallon size, as the seedlings grow. Tomatoes planted deep, up to 80% of the stem between roots and the first set of leaves, will develop roots along the stem, which gives them a "leg up" when they hit the garden soil.
You might want to keep a calendar of when you started what, so next year you can adjust your starting times.

What I do is use a 4' fluorescent shop light for light, but I checked the 30 year lows for my area, and 32* was in April, though the frost free date is later. I use TunLCovers for planting out in April, they are double-walled plastic, 18" tall and wide, ~18 feet long. They have seen my seedlings through snow and frosts, and accelerate growth underneath, and also keep rain off, so I use them in advance to dry the soil in the beds before planting. They are also great for squash and cucumbers, I start squash 4-6 weeks early and plant out under the tunnels earlier than I could otherwise, in May instead of June, and in just a few weeks have a robust plant almost ready to bloom instead of just getting started.

Thanks everyone.

I've compared them to other's seedlings that were started around the same time, and they seem to be way behind. Granted, they don't have any artificial light, so I'm not really worried. As of right now, the tallest one is about 2-3 inches tall and maybe 2 wide, with 2 sets of leaves. They were started a little over a month ago.

Marlin, that seemed like a viable option. I potted them up to I think 12 oz cups, but they really didn't have much in the root department, most likely because of the limited light. I think they'll be ok for another month where they are.

Hemnancy, I hadn't considered tunnel covers. Very intriguing though :). I thought I could do wall o waters, but I would need quite a few of them. I think a tunnel would be the perfect solution, and they just might give me some early maters.

Thanks for your help everyone.