Tbh. DIY is my best advice for DMs. As with CR of mobs, the rarity of magic items and their impact depends on context, namely what is the party composition, what is the general frequency of magic items what (if) are the predominant kind of opponents a party encounters.
e.g. a wand of hold person is of no use in a campaign where mainly animals, demons or undead are encountered, so every classification via rarity and any possible item-power deducted thereof is a rough guess at best.
Some items to be especially careful about to hand out:
Any items which drastically alter AC and worse might stack e.g. ring/amulet/cloak of protection
Any magic armor with high plus e.g. +3 shield.
Any items which allow for easy or uncommon way to travel (e.g. bag of holding, boots of flying, ring of featherfall, waterbreathing items etc.)
Any items which allow trivial access to other planes like foldable portal, codex of infinite planes.
Any items which expand senses, like a crystal ball or a gem of seeing.
Items which have no big impact on settings: +1 weapons, +0, weapons with a +1d4 damage, 1 shot spell scrolls, items which give up to +2 on a single attribute items of <energy>- resistance, magic ammunition etc.