you can buy neodymium magnets in all kind of shapes and sizes on the internet, the ones that come with the DR are 30 X 19 X 3 mm in size.
Using round magnets should also not be a problem, if you get one around 1" in diameter.
The main thing to look out for are polarity, you want it so they stick together like stacked coins ( having the magnetic poles on either side ) VS each half of the shape being one or the other polarity so they stick together at the end.
Many also come with dual sided tape ready to go i see in Amazon
With these super strong magnets it is important to not let then "zip" together at the speed they like ( instant ) CUZ that might make them shatter, ideally you want to slide them on and off each other, the strong ones you cant pull apart just like that, either CUZ they are large and very strong, or you simply can not get a hold of them good enough to do that.
I find that i have to buy magnets every now and then, really once you got some and find out what they can be used for ( i for one also use them to hold 2 things together while glue dry, if not a too thick thing they do that just as good as any clamps you might have )
Well then it get hard to be without them.
Zip ties ( assortment )
Duct tape.
Neodymium magnets
Those are 3 nice things for a man to have around the house.
The magnets you of course have to be very careful with around little kids, the small ones are easy to get down, and they can create all kind of havoc if they can latch on to something from the inside.
I for the most get a mixed package now and then, so either a square mix pack or round ( smaller ones under 1/2 inch for the "big" ones )
There is a hobby called magnet fishing, they do that with these magnets,,,,,,, bigger ones with a pulling force of 2 - 300 KG, so you do not want to latch on to a old car wreck in the river / lake, CUZ they you really have to put your back in it to make the magnet let go of whatever.