You need a hexagonal shaped tube, like the one I'll link below. I use one of those and it can fit that type of mat just fine.
https://www.amazon.nl/Gamegen-Playmat-zwart-kleur-GGS49001ML/dp/B084TMFSHK/ref=asc_df_B084TMFSHK/?tag=nlshogostdsp-21&linkCode=df0&hvadid=572425618042&hvpos=&hvnetw=g&hvrand=16708907020407641314&hvpone=&hvptwo=&hvqm...