High voltage relays are likely to be a bit larger just because their contacts have to be kept farther apart to break that voltage reliably.
Your best bet for size and reliability is a Tyco contactor, like the Kilovac series. They're pretty small.
But you also have to look at the current rating of the contacts, since if they're to able to handle the current you'll be putting thru this relay, it may fail catastrophically and either break your circuit as it melts, or weld the contacts together so it cannot break the circuit anymore and do it's job.
I got cheaper 12v80A relay on the net and it worked for some time but as it failed a few times either because of the touch button function that cuts the power or somehow got pressed or by vibrations it did finally cease fully and made a mess for me to solve in the last day of the season. I tried to reset but to no avail. I checked maybe 30 minutes later and it was working again but I mean as a product and its function to be a safety cut-off. It cuts off itself at ratings lower than it was build for. I would not go with the cheaper option again. I need to source a new one for the next riding season.