Shoe Tricks!

I've posted a lot about shoes, but I specifically want to know your tricks for heel slippage. My left foot is a size larger than my right and I really don't want to have to buy two pairs of shoes for the different sizes...I have to cater to my left or else my toes will jam in the front. I wear prescription orthotics so those already help with taking up extra space but do y'all have any special ways of tying your shoes for this? Or know of any places where you can buy two different sizes? Might be a long shot. TIA!