It's a tricky situation. Because people can use the same argument either way.
In the end, a ring is just a thing. And while it is very easy for someone anonymous to come online and say it is disrespectful or hurtful to want anything other than what he does or don't give you and you should happy with what you get (or don't) because just doing something to please you makes him unhappy well, I'm not sure how that a good relationship marker either. One person shouldn't have to be miserable at the expense of the other, him or her. And you can use the same argument that he is disrespecting you as well by asking you to forgo something you may find important...and end up in the same fruitless and pointless position.
I've been married, and divorced and married again. I had no rings in my previous marriage. This time I do. I have also changed rings (stones and setting) more than once. When I did upgrade (I'm done now) it has always been with deep discussion and his blessing. I always have contributed substantially to the changes because of the kind of stone I wanted (and that was something very particular that only I could choose).
If I were to do it all again, I'd spend more time be very very honest with myself about what I like. I would have gone big earlier. Sadly, I did not know that was what I really wanted until some time after so catch 22 there. It would have been less expensive in the long run than all the shuffling around and unhappiness and stress the past 7 years if I'd known sooner. I would have sold off as much as I could that I wasn't wearing anymore and put that on top of the original budget. But, I think we were both thinking too traditionally and he wanted it to be from him only so that's how it went. At the time, the budget was much smaller not because of lack of finances, but the "mental" allocation on both our parts (for how much an e-ring should cost) was only for so much.
You have a right to be happy as well. A ring is an outward symbol of your relationship and you have to wear it every day you are together, so you should wear something you like, will be happy with too, and be happy to put on every day. (!) It's a celebretory gesture IMO! And well, too may times women are asked to put their personal preferences/happiness aside and "just be glad someone wants to marry you at all" (which I personally think is a terrible mindset but all too common).
If I were in your position, I would sell what is no longer important, and discuss with him your options.
-Pooling resources for an e-ring. (probably my least favorite choice)
- Letting him be in charge of a wedding band (one that you LIKE) and wearing whatever ring you would like with it (maybe getting a ring for yourself that could work on the right hand or left hand as an e-ring.)
- Have you considered a stand alone diamond (or other stone) eternity band instead of a traditional ring? Lots of bling if you are sparkle oriented like I am, but without the traditional connotations of ring and band pair.
- Consider a fancy colored diamond if diamond is what you are looking for! It might be more palatable to him than the traditional "white stone in white metal" e-ring look.

And maybe easier to use as a RHR.
The important thing is to be able to discuss it without anger or rancor. In any reasonable relationship, it seems like you should be able to come to some amicable and workable compromise that takes care of you BOTH.