Did you check the Exchanges forums here? There are several of them - a general exchange and vegetable seed exchange etc. but you'll most likely find them over on the Tomato Exchange linked below. I know both Seed Savers Exchange and Territorial Seed as well as several other seed companies carry them if all else fails. Dave Here is a link that might be useful: Tomato Exchange forum

Yes, you are absolutely correct, it's not a Physallis at all, although it is a relative. What you have there is not a Cape Gooseberry, it's Nicandra physalloides, common name "Shoo-fly plant" This Physallis relative is native to S. America, grows up to six feet tall, and bears the dry, physallis-like pods you see on your plants. It' often grown as an ornamental, and the branches of pods, once dried, do make a nice accent in floral work. The plant itself is toxic, and can be used to make insecticide teas or powders similar to rotenone, or so it's claimed. However, when I've grown it, I've found it susceptible to whitefly, so I question how insecticidal it may be -- perhaps it depends on the pest species.

Never tried this type, but last year I grew a single tomatillo plant, which is just a large groundcherry selected for eating (in salsas) while still green. The plant was zero maintenance, and flowered profusely all summer, but bore no fruit, apparently they require cross pollination. This is not something usually listed on the seed packet, since the assumption must be that a person will grow more than one plant! But actually, according to every source I have read, this whole genus is very easy to grow -- in fact they are common weeds throughout much of the Americas (probably one or two species even native to Michigan). To make a long story short, and as Carolync1 said, if you treat them like tomatoes and peppers (same family after all) they should be a breeze. Enjoy!

I also grew ground cherries a few years ago. You can use pretty much the same techniques you would use to grow tomato starts. They do take MUCH longer to sprout than tomato plants, and they're a lot smaller as well, so I don't think you need to be too worried about them being small. Maybe they need to be a bit warmer? Like cedar said they seem to need warm weather to really put on growth- even warmer than tomato plants need. When I grew them, my plants were healthy but they did not produce a huge crop, and the fruits took a long time to ripen (wait until the outside skin is basically dried up like a dead leaf). I wonder if the seedlings' growth is being affected by it being chilly inside your growing area. If I were to grow them again (I only did it once) I would give them a cloche or some kind of warming row cover until fairly late into the summer, TBH I think they really aren't very suited to the PNW climate and they need an augmented environment to do well.