Good Morning,
Sorry to hear of your Dad's health issues. But there is hope.
As far as the lift for shoes - if you go on the internet and search SHOE LIFT you'll see several companies who provide shoe lifts at reasonable prices. Your dad will need to have his leg measured, if he hasn't already, to determine exact lift measurements.
Secondly, your dad my find using an upright walker is better for his back, arms n balance for walking. I have one and it is incredible. Amazon has the best prices n current reviews. I presently use an Elkener upright walker with 12" front wheels which is good for most terrains. Be your is another excellent brand. Average prices range between $200-$300.
Finally, I was told the same from surgeon regarding no further hip surgeries. The odds of serious life threatening infections is incredible. I had two previous hip infections which lead to near death sepsis.
I hope this is helpful. Please keep us informed of your dad's progress. I wish him all the best.