There are straight horizontal chin-up bars and ones with angled ends. Could we use something to convert conventional horizontal bar into 2nd type? May be attach something to the ends.
Visit a plumber with a pipe bender, an electrician with a conduit bender, or a machine shop with a hydraulic press, or a home renovation centre for a pipe bender to fit the bar you have.
It will take you longer to take your bar to the tradesman than it will take to bend the bar.
You can buy or rent what you need to do the job if you want to do the job yourself.
Don't forget to figure-in the cost of the modification to the cost of the unit. It might be cheaper in the long run to buy what you need instead of one that requires a conversion.