Beseler 23C II Enlarger question

[Tuffythepug]

I'm hoping someone with a little knowledge of this subject can help me out on this.
I have a Beseler 23C II enlarger which I've owned for about 25 years. It's been stored for the past 15 years and I just got it out, along with all the rest of my darkroom gear, and I've begun setting up another darkroom in my home. I have the Nikkor lenses for 35mm and 2 1/4 x 2 1/4 and negative carriers for both formats as well.
My problem is that I am now shooting 6 x 4.5 (Bronica 645 ETRS) and I don't have the necessary negative carrier for this format. The correct carrier is rare but can be purchased on-line. A new one is listed at over $100 ! So the question is this: Is there a reasonable alteration I can perform on the 2 1/4 x 2 1/'4 carrier to cut the opening down to 645 dimensions ? Preferably it would be a fix that could be reversed if I shot 6x6 at some point in the future. Or alternately, can a negative carrier be fashioned out of heavy mat board or some other easily workable material. I don't have a metalshop and I'm not good with fabricating with metal anyhow.

Does anyone have any experience fashioning this type of item or altering the carrier I have now ?

Or, I guess another question would be; Does anyone know where I can buy the proper one at a reasonable price ? I believe it is the mfr. #8048 model carrier I need.

 

[wsetser]

I've not done it with a Beseler negative carrier but a have modified Omega carriers. If you have or can find some slide masking tape, just use a few strips to mask the opening to fit the negative. If you find a good deal on a new carrier or need to print a larger negative, remove the tape and clean off any residue.