Stick-on heel grippers should be available in any shoe store, if that's where your problem area is.
Tongue pads are harder to find - they're available for online ordering, or if you have a swimsuit with bra pads that you don't use, those work perfectly under the tongues of my running shoes.
Depending on how your shoes fasten, you may be able to set up the ratchet to close tighter on your smaller foot.
Everything I know, I learned by crashing.
2007 Cannondale Synapse Feminine 3 - SI Turbomatic Gel Flow
2003 Trek Navigator 200 - Specialized Jett 155