There are no special fittings for clamping the plastic conduit to the pole. When using direct burial cable, manytimes, I slice the pvc conduit lengthwise with a table saw and a carbide blade, choosing to place the cut out channel area next to the curvature of the pole and strapping it to the pole. In some cases, I have tried 16 gage 304 stainless steel wire wrapped and twisted over both the pole and the pvc conduit. THis is hard to see from anywhere except up close.
3M grey electrical tape used to be obtainable from Home Depot, but the only place where I see it now is at WW Grainger. It actually lasts longer than wire ties and is neat and hard to see.
They make a PVC weather head cable entrance head, but I really don't like it, since it is bulbous and ugly next to the pole.
I much prefer to make a custom cap out of a grey PVC cap especially made to fit the conduit. These are available at Lowes. Basically, I use a bans saw and cut a vertical slot at the width of two cable diameters off the side of the cap. Where the cable comes out of the conduit, I loop it back downward to drip off rain. Then, I fill about 2 inches of the top inside of the conduit end with a duct seal. Grardener Bender (GB) duct seal available at Home Depot at $2 for a one pound block is a good brand to use. This stuff is like non hardening putty. Then, I place the customized cap pver the top end with the two cables coming out of the side so that it goes down all except for one cable diameter. When I'm satisfied with the fit and the direction the cable comes out, I place just one small 1/4 inch swab of pvc cement one the bottom edge of the cap and push it down on the end of the conduit. This is enough to hold it in place indefinitely, yet I can break it loose, if I ever need to with an upward wack with a block of wood and a hammer, without damage. The cap can also be reused.
As far as the length of the movement loop is concerned, I'd just make ot longer than necessary and tape it temporarily in different positions, until I can trim it for the optimum length.