Here's what I ended up using on my last re-assembly (30 mins ago as of writing this). This Apple Watch S5 (44mm) adhesive is pre-cut, and fits the corners of the PTS reasonably well. It is however a bit long, so I cut it about 3/4 down, applied the top half, and then cut the bottom half to size and applied it to meet flush.

It's also worth noting that this adhesive is quite thin, and needs to be triple-stacked to make contact with the top frame. I found two was too thin, whilst four was too thick! Fortunately, they come in packs of 5.