I don't think this is possible but...

First Question: I don't think you can make the boomerang or arrows cost magic, but maybe there is a way.

Second Question: Are you asking about are there items that only certain enemies are likely to leave behind? If so, here are some examples of common enemy sources of items

Bombs--Blue Octorocks, Blue Lynels, Blue Moblins, and some of the dungeon enemies

5-Rupee Coins--Red Leevers, Blue Tektites
Hearts--Peahats

As far as how to make certain enemies drop certain items, I do not think it is possible. But you're wondering about magic jars, I know that Keese and Gels drop these a lot. Of course other foes can do so too.

I think it's only Tribble Gels and Keese that drop lots of magic. But don't quote me on that.

Oh, Red Darknuts and Some Wizrobes, and most enemies that use Cset 9, will drop magic-related restore objects. 😉

Is there any way you can get items to cost magic that normally don't (for example the boomerang or arrows)?

And in a related topic, is there any way to increase the amount of time an item drops (like magic jars)?