Does anyone have a recommendation for a good air purifier here? We live next to a main road that trucks drive through at night and it's causing a lot of coughing issues in our home from the pollution.

I'm an hour from you (by air) in Thailand and also need an air purifier but we only have expensive Japanese models here.
If you find a room-size model for around $200 could you send me your retailer's details?
I'll have him ship it by road.
Thanks!

You need an air purifier with a Hepa filter. You want one with a washable filter.

In Beijing I would wash the filters every week in the two units I had. Sorry, forgot the brand.

I own this one, detail.tmall.com/[...]

though, I paid a bit less for it. I think I paid less than 700RMB after shipping in 2012. I think it's really only suitable for a single room though, not a whole house.

A few people I know bought some "xiaomi" branded units which they seem to like. detail.tmall.com/[...]

As far as I know a "HEPA" filter is just a donut shaped cylinder. I don't think it matters what shape the filter cartridge is as long as it is of decent quality and has sufficient surface area.

HEPA is a standard, a proper HEPA filter is one that can trap 99.97 percent of dust particles that are 0.3 microns in diameter, and HEPA filters come in many shapes.
The benefits of the HEPA standard are well documented.

There are PM2.5 sensors available for purchase, so if there is any doubt that a non-"HEPA" certified filter is working or not there are ways of confirming.
Aside from getting a filter that actually does what it's supposed to, it's nice to have one that is simple and affordable to replace. I don't think it's necessary to have the US government stamp of approval as long as the filter meets similar specifications. Basically all the air filters claim they remove 99.97% of PM2.5 from what I h ave seen.
I live in an area where PM2.5 levels regularly exceed 300. The filters I have work properly so long as the cartridges are replaced when spent. I think they run about 80-100rmb.