I'm not crazy about the stock camera strap that comes with the Holga 120 camera. The stock strap is too short, too thin and the little clips on the strap often come undone at inconvenient moments.
A better camera strap won't fit on the small lugs on the Holga 120 camera body, but by using 1/2" split rings (these are small key rings), you can attach most any camera strap you like to your Holga 120 camera. I picked up the inexpensive strap from my local camera store, Glazer's here in Seattle. If you can't find a strap conveniently nearby, look online. (Check my Where to Buy page for specific recommendations)
This modification doesn't work well with the Holga 135 camera, since that camera only has a single attachment lug for a small hand strap.
I also don't recommend this particular mod for the Diana+, F+ or Mini cameras. When I tried this on one of my Diana camras, one of the plastic lugs eventually cracked, probably due to stress placed on the lug with the hard metal split rings. A better solution for the Diana cameras might be to use a softer material that won't over stress the plastic lugs on the camera. I think plastic cable ties would work fine for that purpose.
This is a very easy mod to do.
The key ingredients to this Holga mod are two 1/2" split key rings that you can get at most any hardware store or place that makes keys, and a camera strap of your choice that has 3/8" attachment straps or clips. You may already have an extra camera strap that you can use with this mod.
With the rings in place, the new camera strap is attached to the split rings.
You may want to tape the clips to the camera or do the Velcro Mod on your camera, to be sure that the strap won't pull the clips open when bouncing around in your camera bag or purse.