I need help

When I ordered the cardstock for our invitations I just planned on doing the RSVP as a postcard so we didn't have to get smaller envelopes. Well now my mom doesn't want me to do postcards so I have find 4x6' natural or navy colored envelopes. Problem is I can't find them!!!! They are all 4.15x6.15 or whatever so they can fit 4x6 pictures but I just need 4x6!!! Our cards are 3.7x5.7' so I don't want the envelopes to be too huge for them

If anyone knows where I could find these I would be forever indebted to you! TIA!

I can only find them in white on Amazon. If they are 4 1/8 x 6 1/8 I think it will be fine though! Here's the link for the evelopes on Amazon. .

how about this?
color envelopes