Dan,
how are things over the pond? Haven't been there since 2006 and I'm beginning to miss afternoon tea. We have a couple places here in NYC that try to recreate the experience, AND are owned by folk from the UK, but it only comes close.
Obtaining another Sinaloan should not be a problem as there are many that offer beautiful examples of that triangulum. It's refreshing to hear someone express the good sense it makes to not intentionally cross species or sub-species (with exception of naturally-occuring intergrades of course), and try to make some effort towards preservation of the integrity of specific and sub-specific groups. We can argue all we like and make excuses that breeding true is "boring", but the bottom line is that the hobby will get real screwy if we can't tell one thing from another anymore. And what would potential consequences be? First thing off the top of my head would be the removal of wild specimens to compensate from the non-sense crossings/hybridizations from years past. Some folk will eventually just get fed up enough and seek their own specific animals from the field. My statements may "sound" far-fetched, but even while this mindset has not become the norm, the future may hold some interesting times with regard to the legal aspect alone of keeping reptiles (yet another huge issue...).
This past year alone, I have observed a number of issues with regard to utter confusion as to what certain individuals actually had. Such specimens have included alterna, thayeri, mex-mex, micropholis, blanchardi, sinaloae, and campbelli . . . I'm sure there have been more but the instances I have seen just in this past year are clear examples of tainted lines likely due to crossing/hybridizing. The one that probably killed me the most was learning that the micropholis currently being offered are actually NOT true micros, but rather a crossing of micropholis x andesiana. I have been waiting for true micros for as long as I can remember, but knowing what I know now.......I wouldn't be interested. But that's just me, as some people feel they may very well be the same milksnake. I beg to differ, and will always have that extra space if and when a true Ecuadorian milk becomes available. We missed that boat a long time ago -- and now with the U.S. having a closed door relationship with a number of countries, obtaining true specimens remains bleak at best.
Lastly, I'd had the opportunity to reclaim Pueblans a couple years ago from a friend that I'd given them to prior to entering graduate academia. These animals changed hands and wound up as display animals in an educational mimicry exhibit at an aquarium here in NY. I worked my butt off to reclaim this pair of 12 year-old Pueblans because I'd learned that they were F4 descendants of wild, locale-specific campbelli brought in from Mexico circa 1985. How did I learn this? I happen to be friends with the fellow who actually brought these animals into the U.S. and had recently re-confirmed this fact several weeks ago. Needless to say that I am ecstatic about the old blood I have reacquired, and have every intention seeking out other older specimens to try and mix some other original blood into the line. No worries of Honduran or any other sort of influence whatsoever in these. But had i not been able to do this, I likely would have avoided acquiring Pueblans as far too many have demonstrated unusual traits that scream something other than true campbelli.
Okay, now go and pass it on . . .
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Jerry Kruse 
"One often meets his destiny on the path he takes to avoid it". - Master Oogway