Colvos Creek Nursery lists it in a gallon container. I've never bought from them but they don't have any negative feedback on gardenwatchdog.

Here is a link that might be useful: Colvos Creek Nursery

Thanks, karyn1. Just got off the phone with Colvos Creek (Mike Lee) and ordered their second to the last plant. I'll let you know when it gets here and how it does.
I hated losing that connection to Heronswood. Thank goodness all of the other plants I purchased from them still thrive.

I get it when you say you hate losing your Heronswood plants :) Just wanted to let you know I lost s. glasnevin too over winter, planted many years ago to twine through a smallish maple and also purchased during a visit to Heronswood. I think that week of icy weather in December was just too much cold...dicentra scandens also bit the dust, both the long established established plant in the ground and rooted cuttings in a pot.

The dicentra is now on order from Plant Delights but with the maple now more mature (roots) I don't have plans to try a replacement solanum.