Decent Topbox Alternative To Givi etc

[MEM62]

Givi kit isn't cheap for a reason - it's extremely good.  In the long run it is economical because it lasts forever and you can transfer it when you change bikes just by getting the relevant fitting kit for your new machine. 
If you want to keep the cost down look for used Givi kit on somewhere like Ebay.  You can't beat it.