Creating a bold font

I’m porting an application over to LVGL, the app has one font file and I’ve created 7pt to 11pt versions that I can compile in but the application also uses a 11pt bold font but I don’t have a font file for bold. Is there a way of creating a bold font? or is there a tool that will take the font ttf file and create a bold version?
I tried libfreetype which does allow you to create a bold version of a font but as the display is only 320x240 the rendering made the fonts unreadable. The compiled in fonts with 1bpp currently look the best.

The board is an Atmel AT91SAM9261, we are using v8.3 of the LVGL library.

I tried FontForge and used the filter to increase the weight by 102 em units and it doesn’t look too bad, I had to manually edit a few punctuation but that was it.