OP, first off, I would like to know if you have a relationship with a prescriber who can help you out here. I believe Gabapentinoids are going to be your best bet for mitigating the RLS without prolonging your withdrawal or developing another dependence. A lot of folks, myself included, use these drugs as the primary ingredient in our withdrawal protocol. Gabapentinoids are a class of drugs which include:
Gabapentin (Neurontin) - Not a controlled substance for the time being. This is your best bet from a prescriber if you are entering the scenario intending to be honest. If you walk around town long enough, you will meet someone who has Gabapentin. That's as far as I go with this advice.
Pregabalin (Lyrica) - This is more powerful and predictable in its action than Gabapentin, but it's not likely to be prescribed off-the-cuff for Opioid withdrawal. If you can acquire Lyrica from the street, as it were, do so and buy as much as they have currently on hand.
Phenibut (OTC) - This is an OTC supplement in the "Western World" and can be found in some supplement shops, but is better and more easily acquired from the internet. In my experience and based upon my limited knowledge, Phenibut is a less-potent, less-effective version of the above stated drugs. It will still drastically improve symptoms though regardless.
Clonidine (Catapres) - This is a blood pressure medication, but it can help mitigate some symptoms of withdrawal like RLS and can help make you sleep.
Cannabis - If you smoke and like to smoke, I'm sure I don't need to advise you on how this substance is best used for your symptoms. Eat/Sleep/Drink etc.
Avoid Sedative-Antihistamines like Diphenhydramine (Bendadryl), Doxylamine (Unisom) or Promethazine (Phenergan), as they exacerbate RLS for a large percentage of the population. The medical community will often directly refer you to Benadryl. Don't do it or rather, try it and see how you like it.
This is by no means a complete or concise guide, but it's some food for thought to chew on. Let us know if you have any questions.