Supplies 1/4 Head caps like Evangeline Ghastly Magnets

I don't think there are standardised sizes for 1/4 head cap magnets. They're likely to be different from company to company. - myou need to measure the ones you need to replace and order that size.

Teddy

 

Ah yes, I see your thought process wigs are often designed ot firta range of head sizes (and even then there's a lot of variation betwwen same-size wigs from different companies), head caps are specific to the comapany. or even to the particular head sulpt - and some dolls don't have headcaps, they cave backs of heads with faceplates that attach to them. Welcome to the ongoing confusion that is the BJD hobby.

Happy magnet hunting

Teddy

 

These magnets are "rare earth magnets" as unoa_im_afreak said, or "neodymium magnets", you can find them easily on Amazon, Aliexpress etc.
Find or borrow a pair of calipers and measure the diameter and the thickness (or just use a ruler but it might not be 100% correct), and you'll be able to buy them easily.
You can then glue them in with Loctite Superglue, just be careful with getting the right polarity.

 

Measure the magnet and get it on K&J (Strong Rare Earth Neodymium Magnets - Low prices, Fast shipping, Huge inventory | K&J Magnetics). They have everything on there and are USA-based, locally owned etc so you don't have to buy from Big Evil Store ^^