This reliable site says germination could be 2 - 4 weeks, so you still have time. https://www.chilternseeds.co.uk/item_980B_vigna_caracalla

To avoid condensation leaks use a plastic bag secured with an elastic band rather than a bin and place the pot on a saucer just in case. With a transparent cover in a sunny window the necessary temperature should be achievable without a heat mat. Have you checked with a thermometer inside the cover?

You can also sit the tray on top of your refrigerator until they germinate.

Well, I got one pop up. Found a tray to put under the bin for drips.

Unfortunately, our fridge is enclosed in cabinatery and I didn't feel much heat on top of our freezer.

I think I'll try the bags in a sunnier window for a bit longer.

Then I'll ask for my $ back $7.50 for 6 seeds with only ONE germinating? That's a bit of a stretch!

If you have an older type heating pad which doesn't have a auto off you can use that on low.