As far as I know, there are no reclockers for Firewire. I have heard that someone did a reclocker for USB though and it is battery powered and part of the cable. Rather than buying this, I would recommend the Berkeley USB converter. USB is not my first choice however.
The connection that delivers the best jitter performance now is actually Ethernet, either DLNA/uPnP or RAAT using Roon. Here is a study I did of my own XMOS USB versus my own Ethernet:
It is for this reason that I am not doing any new USB interfaces.
If you were to go Ethernet, you could buy an external renderer and drive S/PDIF to your Weiss DAC. This is the best way to get the full benefits of hi-res up to 192. You may need to use Jriver rather than Audirvana+ however. I have not had good luck running DLNA Ethernet using Audirvana+. Jriver works perfectly and sounds great.
The converter I sell for Ethernet is identical to my Off-Ramp, but has Ethernet input. It is called the Interchange. It will deliver sample rates up to 192 with jitter in the 16psec range, my lowest jitter solution. It must be used with Jriver. $2999.00. A WIFI adapter is also available for $1K. I believe this to be lowest jitter solution on the market.
If you got a micro-Rendu or UltraRendu from Sonore, this would allow you to go Ethernet and then USB to the DAC. The jitter will be dependent on the clock in the USB interface in the Weiss DAC, so this is not my preferred choice. These are compatible with DLNA (Jriver), Audirvana+ and Roon.
If you go Ethernet or use the Berkeley USB converter, I would highly recommend using a good S/PDIF cable:
No sense in throwing away low jitter by using a poor cable.
BTW, the cheapest way to getting really low jitter is to use Toslink from your MacBook Pro to the Synchro-Mesh and my Reference BNC cable from Synchro-Mesh to your Weiss DAC. You could compare this to your firewire connection starting at $1198.00 (with OTL option). 30-day money back, less shipping. This would work with Audirvana+.