If you mean pistols, then this isn't a strength issue but a mobility & balance one - assuming no injury/condition. One your should put a lot of energy into fixing instead of working around as you'll get lots of benefits from it.
1) work on your ankle mobility like your life depends on it*
2) until you sort the mobility out, do the pistols but grab onto something to help you from tipping over and of you need it, to help you back up from the bottom position. Bands, dip bars, a pole, a rack, all work. Try not to become reliant on this, use less support each time as a progress model
You should be right after 4 - 8 weeks and doing these no problems.
*Easiest way is to sit down (preferably well below parallel), move your foot back until your heel comes off the floor, then have someone SLOWLY sit (or put a weight plate) on your knee so your heel touches the ground again (be careful, trying to bridge the gap created by a heel raises too high is a good way to snap a tendon).
Also any mobility wod stuff on ankle mobility.