I bought a little "sewing machine" light thru Amazon. Loads of LEDs in it (about 8 I think) very strong magnetic base, and a sensible length flexible goose neck. Actually made in China, and mine actually came from there, but didn't take very long either (about 10 days if I remember) Cheap too - again if I remember, less than a tenner.
The only reservation I had/have was with the fitted mains lead supplied - about the thinnest conductors on any mains cable I've ever seen in my life! But so far so good, no problems at all, and the mains plug doesn't get even slightly warm.
The magnetic base clamps very firmly to anywhere I like on the Ex21 arm, or indeed, the table.
Was a great buy which I first got on to through a thread on that subject here in the Scrolling section. If I remember correctly the relevant post was by Claymore, but it's several years back now.
A P.S: I bought 2 of them actually, one for me (above) and one for my wife's sewing machine. But the casings on her machine/s are non-magnetic, so I had to rig up a little steel plate up for here to "stick" her lamp base onto.
HTH. (IF you need it, I can probably find the details, but I guess a quick search through Amazon's web pages will locate it OK. Let me know if any probs).
Edit for a P.S. After posting the above I just noticed the word "magnifying" in the title of your OP. The above has NO magnifier, sorry. I do actually also have a magnifying light (with a normal bulb) on an Anglepoise type arm above my saw, but it really is about a million years old and I've no idea where it came from, sorry.