Colin you are at the end of off season and not quite on the shoulder season, but a swell or two might sneak through.
Padang has two easily accessible spots Pantai Air Manis and Pantai Puru that time of year I would not put my any part of my body near them without an anti cholera suit, every orifice in Padang points to the sea via this channel particularly Pantai Puru which is at its mouth.
Banda Aceh north and Banda Lampung at the south end of Sumatra offer better and more options.
Then of course you have 150km off the coast the MENTAWAIs there are great rusty longboarder waves there and being outside the normal season rates could be cheaper but stay at a camp which can boat you to a choice of nearby breaks.
Rates range from cheap to resort expensive , the cheap camps you usually have to catch the ferry over ( overnight) the more upmarket ones often have a speedboat cross which is 3 hours.
Both Banda Aceh and Banda lampung have mainland breaks, this time of year wherever in Sumatra, I would have vaccinations for cholera, typhoid and hepatitis , I would be fully taking antimalarials, as the wet is either still going or just finished , so all the mosquito borne diseases are rife.
I strongly suggest going to a camp as you won't have to try and figure out sketchy roads or explore a lot

I've taken up troll hunting just for fun, instead of a rifle I'll just use a pun! 冲浪爷爷