Try at Handyman at Robinsons.... if it still didnt exist... try to ask their manager if he could order one from their main branch at Manila and when will it arrive here in Dumaguete branch. Or you can buy one at Ebay and other online stores. Be careful with those online scammers or fake stores.
I'm reading your reply at Robinsons now. We'll check out Handyman before we leave. The dive shop at Harolds Mansion had a couple that seemed pricey on the phone. I'll go look. ScubaWorld in Cebu will have some first well of May so it looks like I can get a bag one way or the other..