Here's a $100 livewell:
https://www.cabelas.com/cabelas/en/templates/product/standard-item.jsp?_DARGS=/cabelas/en/common/catalog/item-link.jsp_A&_DAV=&id=0001512012757a&navCount=0&podId=0001512&parentId=&masterpathid=&navAction=push&catalogCode=IJ&rid=&parentType=&indexId=&cmCat=netcon&cm_ven=netcon&cm_cat=Google&cm_pla=livewell%20cabellas&cm_ite=netcon
Judging by it's size, it wouldn't be too hard to remove the center seat (or part of it), mount the livewell (insulating it wouldn't be a bad idea either), and covering it with wood to regain the use of the seat.
ST
https://www.cabelas.com/cabelas/en/templates/product/standard-item.jsp?_DARGS=/cabelas/en/common/catalog/item-link.jsp_A&_DAV=&id=0001512012757a&navCount=0&podId=0001512&parentId=&masterpathid=&navAction=push&catalogCode=IJ&rid=&parentType=&indexId=&cmCat=netcon&cm_ven=netcon&cm_cat=Google&cm_pla=livewell%20cabellas&cm_ite=netcon
Judging by it's size, it wouldn't be too hard to remove the center seat (or part of it), mount the livewell (insulating it wouldn't be a bad idea either), and covering it with wood to regain the use of the seat.
ST