Both Nifedipine and Diltiazem are typically administered in a pill.
Both are Calcium channel blockers, which help relax the muscle wall of arteries and lower blood pressure to promote the flow of blood, so if you've any concerns about existing low blood pressure issues, they'd be a concern.
Nifedipine can also be administered in a topical ointment if you find the pills aren't a viable option.
Regarding prescriptions, I'm afraid that's something you'd need to talk with your care provider about. Each nation's different in this respect, but I expect a prescription would be required.
Chill Burns are a blood flow problem, most often associated with cold weather where blood is remove from extremities and pool in one's core region to warm vital areas, so we always recommend warms. Have you tried hot or trauma blankets on your arms or legs?
I used them to treat shock responses, for which heat and pressures help alleviate, but they can also promote blood flow via warming one's extremities.