quick, cheap way to get a good seal and a strong plunger from my longshot ?

Is there any way to achieve this?
I just found out i am going to uni (Ballarat)
So i want a better than stock seal, and a good way to reinforce the plunger.

Any help is greatly appreciated.

Open up your longshot, add an extra O-ring to the plunger head or if you don't have one the right size, use teflon plumbers tape and wrap it around the groove about 2 or 3 times then put the stock O-ring over top. Then take some foam, trim it so it fits the size of the head and superglue it to the plunger head. Don't forget to put some lube on it so it doesn't wear out as quickly and generally works better. BTW, questions thread next time.