I had been wanting this Hoya for some time after I first heard about it back in 2016. Little did I know that I had purchased it in 2018 under a collection number of GPS 7-35. I found this out when I researched the accession number. From the description by Michele Rodda and Nathalie Simonsson:

Distribution and ecology.

“Hoya isabelchanae is only known from the base of Gunung Boliohutu, Sulawesi, where it was collected as a sterile cutting in 2002 and brought into cultivation at the Royal Botanic GardenEdinburgh where it regularly blooms in a heated greenhouse from May to October. The species was collected in primary forest and it was growing in shaded but exposed area on a decaying tree 12 m tall. A further collection is widely available in cultivation under Gerard Paul Shirley number GPS10161 and 7-35 http://www.paulshirleysucculents.nl/shop_hoyas.htm [accessed on 24 June 2016]. This accession is apparently also from Sulawesi but no further collection information is available.”