I'm after a small(ish) rack top bag - i.e. one that sits atop the rear pannier rack.

The one that has caught my eye is the Topeak DXP Trunkbag:

https://www.topeak.com/global/en/pro...8-trunkbag-dxp

I like the fact that it can expand if required and has panniers if extra capacity if needed. However, most of the time it will remain nice and compact.

Are there any other similar bags that I should consider?