Hey there, fool4flowers, I am not familiar with the opo squash, but maybe you can find the variety you are looking for at

Evergreen Seeds

or

Kitazawa

Hope this helps.

whoops! Just looked on their website, I didn't know Opo was another name for bottle gourd. It looks like they has quite a few varieties, some that are fat at the bottom.

Opo Squash

Thank you so much, it must be some form of bottle gourd since that is what I saw on the one site that looks nearest to it. I was excited to find an opo at the grocery store last night and brought it home and cooked it. It was similar in taste and texture but more bitter and the one I bought was much smaller than what we grow and straight not rounded at the bottom like ours. I think I will try another batch and see if I can get more to germinate. I hope its not too late. The one plant that germinated is not doing well so I will plant more in another spot. I had it growing up a tree and now that the tree is leafed out it is in too much shade. We used to grow them up a telephone pole at our shop but the deer get them over there. I appreciate the help and will post a pic if I can get a squash this year, lol. Will be happy to share the seeds if I can get more. It is very good and the flavor is mild. It takes up all the flavors of what you cook with it.

Maybe you can find the seeds from a a source in the Philippines, since it seems as though there are many different regional varieties. I've wanted to try bottle gourd after seeing lots of Indian recipes calling for the vegetable. Seeds of India also has two varieties of bottle gourd. On is 1.5' long and one grows up for 4' (That's huge!) I have had excellent germination with the seeds I bought from Seeds of India, including ridge gourd and bitter melon.
Post some photos later on. I'd love to see-em!

Seeds of India

The filipino gourd you are looking for is called fuzzy gourd or ash gourd. Some people call it wax gourd. Its scientific name is benincasa hispida. Seeds of india sells it.