Classroom science equipment

Not sure in your case, but I find it easier just to go online and order what I want and have it shipped here. Then I know I get good quality and get it fast. Might check it out.

Yeah, I've looked into that, but it gets quite expensive. Just wondering if there were any more local options!

This is really out of my wheelhouse. But in general terms I find it can get quite expensive buying the cheap garbage they sell here that only last a few days. And I do appreciate and understand their are unique economic concerns for all of us. I think the company on
the West coast in California charges $1.25 a kilo to ship to HCM. I can usually find most of what I need/want on Amazon/ Many times they ship to my forwarder for free. But you have looked into all this. I wish I could think of someone to send you to that might know.

Amazon has the wave tank for $71. Don't know what price range your looking for.

It sounds like you are teaching a science class but doing it on your own rather than through some established school.  This is kind of a long shot but you might try Nhà Sách Đại Trường Phát.  They are at 207/6 Nguyễn Văn Thủ, Đa Kao Ward in Q1.  They are mostly in the business of providing ESL books on contract to government schools and language centers but they seem to carry other instructional tools as well as classroom equipment like desks and chairs.  You will need a VN friend to negotiate their website as their usual target customer is Vietnamese but here it is:  http://www.daitruongphat.com/