May I suggest you take a look at the Alien Gear Cloak Tuck 3.0 IWB holster for your Shield. They also make an OWB holster, which I have not worn. But you and I are the same year model, and I've been carrying one of these holsters with Shields for about six months now and find it to be the very best choice I've ever used for IWB carry. I have tried and worn MANY holsters over the past 50 years. This one is the most comfortable I have worn, and it does the job intended as well as any I have ever used. I also like OWB holsters, but for carrying concealed, IWB is best.
In my experience, a larger size of pants is not needed with this holster (unless the pants you are wearing are extremely tight!). You do need a good double thickness gun belt for your pants. AG also sells a good looking belt, but I have no experience with it. This holster is very adjustable for height and cant of carry. It is very secure on your belt and waist, and the neoprene backing portion is incredibly comfortable, especially if things are hot and sweaty. It spreads the weight over a wide area on your waist. It does take up some real estate on your waist line, but trust me, this is a positive attribute. It will take some getting used to, as does about any holster you will wear, but it requires little break-in of the holster, just a bit of break-in for your your body! Bonus is that you can purchase finished kydex shells for many different types of guns that will fit the neoprene backing portion. It is also made for some revolvers! AG is and has been a great company to do business with. You can call or email them and talk to them and they will happily answer your questions and give you their best advice. I highly recommend Alien Gear and their products!
BTW, I'm a bit taller than you, but my waistline is likely as big around or moreso than yours! And I also have some body real estate that protrudes over the waistband of my britches. The AG holster still works very well for me!