The easiest place to locate a 12v battery would be from a local AutoZone, or autozone.com. The prices vary, but a low end model with a year warranty should run you about $39.99 USD.
You can purchase cheap Olympus batteries at batteries4less.com. Another great site for saving money on batteries is atbatt.com. Locally, you can try Batteries Plus.
The batteries you are looking for can be purchased anywhere and do not need to be special ordered. Some retailers I know of are Radio Shack and amazon.com.
You can purchase these batteries on any legit website that sells things. Such as eBay, craigslist, and amazon. They are trust worthy sites, and give you plenty of options on finding the cheapest.
There are a wide variety of online stores that sell 12 volt batteries. The online sites for Wal-Mart and Staples, along with Amazon, for example, each sell this product.
Four 12V batteries may not be connected end to end to obtain 36 Volts. But four 12V batteries can be connected end to end to provide 48V and push 36 amps. The actual answer to your question suggests that you drop one 12V battery and use three, not four 12V batteries end to end to obtain 36V.
One may purchase cheap Delco batteries from a number of websites including "CarBatteryWorld", "AcDelco", "Amazon", "eBay" and "BatterySales". One may also consider looking at alternative brands that may provide the same amount of energy for a lower price.
It will ultimately depend on the model of truck you have. I would recommend places like Batteries Plus, Interstate Batteries, and Optima Batteries. Maybe even Wal-Mart too.
Yes, you will need to install a second 12V battery in series with your existing 12V battery to supply 24V to the winch. However, to keep them charged, they have to be charged in parallel. You'll need a schematic to do this correctly and not damage the winch or batteries. I recommend you contact the winch manufacturer for a schematic. It might be best to purchase two new 12V batteries to operate the winch and not tie into your Land Rovers battery. I would purchase "deep cycle" marine batteries such as are used in boats and RVs. These will give you the best performance They are available anywhere batteries are sold.
There are many places on the internet that you may purchase RC lip batteries. A few websites are www.maxamps.com/, www.cheapbatterypacks.com/, and www.rclipos.com/.
You can purchase 12V batteries from many different locations. Good prices can be found at Wal-Mart or Target. Online, you could try Amazon or EBay. You could even try local dollar stores.
LG Chocolate batteries can be purchased from store such a Best Buy. Cell phone stores that carry the phone will also be able to help with the purchase of replacement batteries. The batteries can also be purchased online from Amazon or Ebay sellers.
without knowing exactly the types of batteries you are talking about but generally marine batteries are a higher quality battery and have higher amp hour ratings which basically means they can turn the stater for longer