It’s sometimes called a darning foot, or open toe foot Any sewing shop will have them, they’re common. Looks like this.
Most machines have the little curved ‘arms’ that hook around the shank (the bit where you screw in the needle) and are held in place by a screw on the left, you can see them in the picture above.
Look at the foot that is currently on your machine and you should be able to see what kind it is. Shoot me a picture if you’re not sure. I’ve owned three different brands of machine over the years, Toyota, singer and janome. The feet have been interchangable, in general any brand will do.
You also need to check if your sewing machine can lower the feed dogs-almost all of them can. Feed dogs are the spiky metal bits that sit under the needle, they push the fabric along. When you FMQ you don’t want anything pushing the fabric, except your hands, which is why you lower them out of the way. Google how to do this for your machine, or check out the manual.
You can buy feet very cheaply from AliExpress if you’re not in a hurry-you can also get big sets of machine feet with far more than you would ever use.
#Aliexpress € 21,60 31%OFF | 62/52/48/42pcs Sewing Machine Presser Feet Set Rolled Hem Feet for Brother Singer Braiding Blind Stitch Darning Presser Feet
Vintage machines sometimes have feed dogs that can’t be lowered, in the case you can get a darning plate, that fixes over the dogs and stops them coming into contact with the fabric. There is a discussion about this here
This is a really good video that takes you through the whole thing as a complete beginner.
Hit me up if you’ve any more questions