So, you're a spellcaster who has taken a couple level dips in other classes or took a prestige class that doesn't give you full caster progression. You're going to miss out on the spell levels, that's the price you have to pay. But do you have to have a lower caster level as well? You could have had the foresight to start with the Magical Knack trait or ask the GM to allow you to grab the Intuitive Spellcaster feat (which they totally should). But what if you can't really afford the feat? Here's a magic item that I came up with:
Gloves of the Heightened (insert class name here)
Price 6,000 gp CL 8
These magical gloves are attuned to a specific class. When these gloves are worn by someone that has levels in the specified class, their caster level in that class gains a +4 bonus as long as this bonus doesn't raise their caster level above their current Hit Dice.
Construction Requirements
Craft Wondrous Items, creator must have 8 levels in the associated class, 3,000 gp
Alternates: this could easily also be an ioun stone for double the cost, be a ring by changing the feat requirement, and/or give a higher or lower bonus. To find the base cost the item, take the bonus squared and multiply by 375. CL of the item and levels in the requirement are double the bonus.
I loosely based the cost of this item off the Dark Blue Rhomboid.