How do I restore my iPhone if my lock button is broken?

My phone lost charge, when I plugged in the charger the 'support.apple.com/iphone/restore button showed.

I followed the Apple instructions ie. quickly pressing volume up and down but I'm then stuck when it comes to pressing the side/lock button as my lock button is broken (currently using AssistiveTouch to lock my phone)

Is there any way round this other than booking in a slot at my local Apple store to repair my iPhone?