If you want gear to keep your pup warm while you are out hunting you'll have to make a bit of an investment, but if you're just trying to keep him more comfortable for an hour at a time in winter, these are some options that have worked for me:

Gooby Stretch Fleece Pull Over Cold Weather Dog Vest, Black, 4X-Large https://www.amazon.com/dp/B01F38Q87M/ref=cm_sw_r_cp_apa_us8zyb2R27JP1

Kurgo Chilli Red Outdoor Coat Loft Dog Jacket, X-Large https://www.amazon.com/dp/B00QL4DQQE/ref=cm_sw_r_cp_apa_Dr8zyb018P3XG

Zack & Zoey Polyester Fleece Lined Dog Hoodie, XX-Large, Green https://www.amazon.com/dp/B0062H9F9W/ref=cm_sw_r_cp_apa_eu8zybM6TZSS7

The fleece vest is very stretchy/forgiving and he will wear it for a day or two straight without issue (it's pretty light). The puffy vest is great for colder weather and adjusts well to different sizes, and if it's bitter cold I might even put it on over the fleece. I wouldn't leave that one on all day though unless you need it. The hoodie is cute but the chest is more restricting than the others so I would try the other options first.

I definitely recommend measuring your dog to make sure you are selecting the right size. Ours will happily play outside in the snow for 40 mins with a vest on, but only 10 mins without. If there is no snow he will stay outside over an hour easily with a vest.

Good luck!