Crash beam bolt size - replacements

[Walliethefrog]

Hi all I'm looking to take off my rear crash beam to clean it up, rust proof then recoat it. My hope was to take it off to do this so I could do the rear body too.

Two of the bolts are (were before me) completely rounded on the crashbar to body. No issues I have the tools to split them/ cut them off. I just have no idea what size they are and the diagram Toyota codes don't generate much online for me to be able to locate the correct bolts/nuts I know the ones on the outside are 10mm into captive nuts.

I know I could just cut them off and drill them out but considering it's a semi structural piece (in the event of a crash) I'd like it to still be as close to OEM as possible.

 

If anyone has had to replace it and knows the correct sizing that would be appreciated

http://www.japan-parts.eu/toyota/eu/2010/aygo/kgb10l-agggkw/2_101510_001_302W/body/5202_rear-bumper-bumper-stay