go to www.tayna.co.uk and put your reg. no. into the robot, check this matches your bike's current battery - you will get some suggestions but click the "see all batteries in this size" to see many more options
for me, the Exide AGM battery is the sweet spot in terms of price v reliability but there are dearer options from Yuasa, Westco etc.
Just last month I change the original battery in my '14 plate F8GS.
I got a Motobat item. It has a slightly different set of dimensions that had me fabricating a small spacer plate to prevent fore & aft movement, but overall it fitted well.