I have an old round Diawa baitcaster that the plastic knobs have cracked. I think I am going to replace the entire handle. My stock one is straight and most of the new ones are that bent swept handle design. Will this bent style work ok or do I need to stick with the straight style? Also is it ok if the new one is slightly longer? I just want to make sure it will work before I order one. Thanks.

Not knowing the reel model it’s tough to give accurate advice. You said old, so newer bent handles will most likely not work with strait star drag knob.  
 

 

borrowed a (bench-built) Millionaire photo from @redmeansdistortion

note bent handle also needs matching bent star drag.  

 

here's a straight (new) Avail handle on a different round reel.  

 

Yes, mine is similar to the red Diawa Millionaire above. Mine is a Diawa Millionaire cv-z model 203 A. I guess I need to stick with a straight handle unless I can find a matching bent star drag somehow. Thank you for the information.

Bulldog1935, where did you get that straight handle  with blue knobs in photo above? Looks very nice.

That's Avail power handle T4S (complete kit). also sold as bare handle.  But with lower gear ratio, you would likely prefer shorter Avail S-Trad.  

Note that the T4S takes Shimano-A/ Daiwa-S knobs, but S-Trad only takes matching (short) Avail knobs.  Both handles are very light, with titanium knob spindles.  

Here's S-Trad on my Headhunter BC620

Maybe @redmeansdistortion will chime-in with Daiwa SLP parts. 

The star wheel from a PX68 is curved and fits perfectly. This SW 103 has a PX68 star with an Alphas Air handle.  You can get the star from Japan Tackle either in gunmetal/red or black/silver.