The Jubilator Activator can be obtained in Survival Mode in mostly the same ways as in the campaign, although it can be a bit tricky:
You can buy it from the Odds & Ends Shop (if offered)
You can also obtain it as loot from Dig Spots (Uncommon-Rare)
You should technically also be able to obtain it from an actual Jubilator by immobilizing it with a Shock Grenade, bashing open the hatch at the back and using the Extractor to extract the component. I am not sure if this is actually possible since I haven't seen any Jubilators in Survival Mode.
As for the Jolly Brolly, it is only obtainable if you pre-ordered the game and in that case you should have received a code which, when entered, will allow you to find it in the Pneumatic Stash.
It really doesn't become much easier than that. In order to find Yams, you just have to keep looking until you find one. In addition to Hamlyn Village, you could also try searching around the Garden District, as you can sometimes find Yams in fireplaces and campfires there. In addition to that, you could also try burgling houses.
As for phytosteroid, I'm not sure if I remember this correctly but you could try looking in the Apothecary, as they have a collection of certain drugs.