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Any place that sells the Japanese x...

Any place that sells the Japanese x...
Any place that sells the Japanese xstr handbooks also sells the Jap xstr sub guide. MCM sells them. The D.A.T.A. people used to sell their master xstr guides, but they were pricey. They may still be around. I am old fashioned, I use books.  
A good Japanese transistor manual is very valuable. Look up your type and see its specs, then look for something similar. I also have a Motorola selector guide. They are now called On Semiconductor, but I bet they have a selector on their site. You look up what you need usually from lists sorted by package type, then by voltage and current. I also use an old RCA guide - a short form catalog really.  
None of these suggest subs, but they will tell you what your original part is. Experience has taught me many types I can use as general replacements. And in the manuals, often there are similar parts right above or below your original. If I have a 120V, 10A power xstr, chances are the 140V, 10A one right nesxt to it will work fine. A TIP42C will always work where a TIP42A was.  
In the MCM catalog there is a page in the semi section of suggested types. It is a chart with section for each package types and suggested ones for each along with some minimal specs like voltage, current, wattage. Handy  
I have favorite types for each package myself. I stock MJ15024,MJ15025 for big power TO3s. I no longer stock 2SD424 and all those big Jap TO3s. In TO220 I stock some TIP41,42 types and some MJ1503x types for higher voltage use. I don't like to sub US for Jap and vv. for small signal xstrs - TO92s. The pinout differs so why screw around. You can stock 2N3904,3906 for small voltage ckts. I use 2N4401,4403 myself. MPSA06 is a great 80V, .5A part. The MPSA43, 92 types are good high voltage ones. Low noise parts like MPS8087 and similar are handy. For Jap signal xstrs, 2SA933 and 1015 cover most PNP and 2SC945 and 1815 cover the NPN pretty well. For higher voltages there are others.  
I organize my drawers into groups by package type. And I write the basic specs on each drawer front. SO if I need a TO220, I can see what else I have and select a sub easily. I tend to stock cetain parts for specific brands, but they can be useful in other applications as well. FOr example, I stock 2SC3298 and 2SA1306 for service to QSC amps. When friend KB needed a sub for 2SC22238/2SA968 in a Hartke, we found those have the exact same spec as my QSC types. He had them too, so work progressed.  
Most of what I stock has some original reason for being here, but organizing things the way I do makes my collection more valuable as substitutions as well. My collection of semis is pretty large, but many of them do not get used a lot, so a dozen types on your shelf make a pretty powerful replacement series.  
ALways look at what you are working on with subbing in mind. If some xstr type is used as a signal xstr in a 20 volt circuit, it will work fine in any other 20V signal circuit. Keep them in mind.  
It ain't software, but getting to know your parts turns any parts collection into a replacement series.

dazco yea...... --