My new to me 04 Honda CR-V has seat hight adjustment for the drivers only. My wife finds the passenger seat to low. Has anyone made a modification to the seat to make it higher? Perhaps some blocks or such?

 

If you have a little metal fab skills it would be pretty easy to make some brackets to raise the seat. Honda seats pretty much always vertical brackets so you can't just use spacers and longer bolts except for the rear bolt near the center of the vehicle. I'm not familiar with the 02+ crv's though.

 

Can't she just sit on a cushion? I know it sounds crude, but the seat is a really important part of the safety aspect of the passenger. Using lower grade/longer bolts/home made brackets may cause adverse effects in the event of a crash. I've seen those home made brackets for racing seats let go during a high impact crash. The results can be terrible.

If you really love your wife, you will get her a booster cushion.

 

How much higher? Mabe a few washers

 

You do need to have pretty good fabrication skills, but if done properly making a seat sit slightly higher can be a perfectly safe option.
I grafted seats from a generation 2 CR-V into my generation 1, by cutting the relevant parts (the mounting points) of the gen 1 seats and tig welding them to the brackets of the gen 2 seats. Believe me, they wont break in an impact. My seam welding is of far higher quality and strength than Hondas original tack welding!