Hi Anolis! Welcome to the forum!
I do sell and trade my bulbils, bulbil formation starts about now, and final harvest is usually between December and February.
D-Grower
My yam collection (including bulbifera) has grown and keeps growing. This year has been a bit hectic, but if all goes well, I'll have some stuff available during harvest time.
As for Lerén, I have a spare plant I can send now. My recommendation is to dig up the plants as winter approaches, prune off the feeder roots, tubers and top growth, and pot them up indoors for the winter (they don't mind the shade). If there's a lot of plants, you might dry them out for a couple of days after pruning and store all the rhizomes in soil indoors. They can look a bit dead for a long time if you go for the dry-out method, but they'll eventually resprout.
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Edit: My bulbiferas are edible. I've eaten them, my family's eaten them, my grandma's eaten them (I wouldn't be surprised if her dogs have eaten them). Whether hard and underripe or past their prime and bitter, we've never been poisoned. They get bigger in their second year. Pick 'em large for a tender tuber. Eat them fresh for best (potato-like) flavor.