To my knowledge there are 4 Runes that provide magic find, and 1 Sigil that provides magic find: (Please note that an effective way to get more magic find is to stack 5 of one type and 1 of another, giving 60% rather than 50% magic find.)

Magic find armor is most easily obtained by having it crafted or buying it, note that the former is cheaper and you need only ask the crafter for the mats. Note that weapons are made from similar materials and called by the same prefixes. The prefix is “Explorer’s”, providing Magic Find, Power, and Precision, and they require a tier of the claw fine crafting material depending on your level in addition to other materials. You can have it made in whatever rarity your budget allows, at level 80 you could probably obtain a entire Masterwork set for under a guild wars 2 gold if you buy the materials yourself and get a friend to make it for you/make it yourself. The exotic set is considerably more expensive as it requires 5 ecto a piece in addition to the highier tier materials.

If that isn’t your speed you could look for armor with the prefix “Traveler’s” as that provides Condition Damage, Power, and Magic Find.For Rings/Accessories/Necklaces you are looking for items with the prefix “Opal” and it also provides Magic Find/Power/Precision. Once again buy the set that fits your budget as the difference in stats between rarities is small.