Lead is becoming harder to get for free. I pour too, and used to get tire weights free, but now more folks want the lead, so many tire shops either save it for specific folks or they sell it.
There's always sellers on Ebay with lead. Prices range a bit, and of course shipping can really add to the price. The purer lead types often demand the higher bids.
There is a guy on Ebay who often has lead for $25, plus $10 shipping, and you get 30 to 32 lbs. I've bought from him several times, with no problems. I'll generally pay up to about $1.65 per lb, but that's my limit. You can go to scrap dealers & probably get some cheaper, but it's going to be dirty & need to be processed to remove the junk. All in how much time you're willing to put into it for the cost.
One more thing, there's a big push to remove lead from all wheel weights. You need to know what you're getting if you go that route. I have some that are zinc, and it melts at a much higher temp than lead, so is really no use. It will also contaminate lead for pouring if you do get it melted. Lead wheel weights are alloyed with other metals such as tin & antimony to make them harder, but can have such things as arsenic in them as well in small amounts, so take precautions.
Bullets, and lithograph lead used in printing are desired, as they're closer to pure, but again, they're in demand & are harder to get cheap.
For sinkers, wheel weight lead is fine if you can get it. I have a lot of molds, and try to use the softer, purer lead for pouring the smaller size jigs, but have been using recycled wheel weights for many years for he larger jigs & sinkers without a lot of problems.