How about you make non-magic bonus items always weaker than magic versions, but make them proportionally cheaper.

For example, instead of a magical +5 hiding cloak of elvenkind for 2,500gp you could get a non-magical +2 hiding elvish cloak for 1,000gp. If they make it, require a craft check and a proportional xp cost too (representing the love and time spent perfecting this masterpiece)

The advantage is non-magical items keep their bonus after being dispelled, disjuncted or inside an anti-magic field. You couldn't replicate blatantly magical stuff like wings of flying or flaming weapons though, just things that provide competence or morale bonuses.